For some liminological and oceanographic studies it is important that underwater samples be taken at selected depths and that such samples be protected against dilution or modification due to leakage of the sampler during retrieval of the latter. One type of sampler used for this purpose comprises a hollow tube, usually open at both ends, and having end closures or stoppers which are adapted to be moved from open positions to closed, sealing positions in response to the dropping of a weighted messenger along the tether line or cable which supports the sampler. The stoppers are latched in their open positions by a releasable latch mechanism which has a release assembly that is tripped by compressive force generated by the weighted messenger to enable the stoppers to move to their closed positions. Such a latch mechanism is disclosed in U.S. Pat. No. 3,949,497, granted Apr. 13, 1976.
Some of the water samplers comprise hollow tubes which are adapted to be suspended substantially horizontally in the water, whereas others comprise hollow tubes that are adapted to be suspended vertically. In either case the closures at the ends of the tube are adapted to be moved from open to closed position when desired and at whatever level the samplers are located.
Effecting closing movement of the closures at opposite ends of a vertically suspended tube presents a special problem. This primarily is due to the fact that the latch mechanism associated with the uppermost closure must be capable of overcoming an upward force exerted by the cable which retains the uppermost closure in its open position. To accomplish this objective vertical water samplers have been fitted with extremely complex latch release mechanisms.
A principal object of the invention is to provide a simple, inexpensive, easily operable, releasable latch mechanism for latching closures at opposite ends of a vertically oriented water sampler in their open position, but which assures release of the latch mechanism when desired so as to enable the closures to move from their open position to their closed position.